This invention relates generally to a heat exchanger or more particularly to a recuperator and more particularly to a method for aligning a circular recuperator core.
Many gas turbine engines use a heat exchanger or recuperator to increase the operation efficiency of the engine by retracting heat from the exhaust gas and preheating the intake air. Typically, a recuperator for a gas turbine engine must be capable of operating at temperatures of between about 500 degrees C. and 700 degrees C. and internal pressures of between approximately 450 kPa and 1400 kPa under operating conditions involving repeated starting and stopping cycles.
Many recuperators are of a primary surface construction. In a primary surface recuperator, a plurality of sheets are stacked in a spaced apart configuration to form a cell. The spacing therebetween form a plurality of donor passages and a plurality of recipient passages. In many operations, the hot exhaust gas is passed through the donor passages and an atmospheric temperature intake air is passed through the recipient passages. Heat from the hot exhaust is transferred through the sheet and absorbed by the cooler intake air. Thus, thermal energy from the exhaust gas is extracted and conducted to the intake air increasing the efficiency of the engine.
In many applications the primary surface sheet used in forming the cell is very thin, flimsy and difficult to maintain a uniform cross sectional area of the passages between sheets. To enhance the rigidity of the thin sheets, the sheets are formed into an accordion type configuration forming peaks or crests and valleys forming a plurality of upwardly and downwardly opening, transversely extending, relatively deep grooves being relatively closely spaced and having substantially vertical side walls or fins. In forming a recuperator using such sheets, the peeks of alternate sheets are aligned and the valleys of alternate sheets are aligned to form the donor passages and the recipient passages. Additionally, many of the sheets are formed with a serpentined configuration to enhance a controlled turbulent which increases heat conductivity and resulting efficiency. In manufacturing such recuperators, the component parts are fixedly attached together by a welding process to prevent leakage from the respective donor passages and recipient passages.
U.S. Pat. No. 5,060,721 issued on Oct. 29, 1991 to Charles T. Darragh discloses an example of one such recuperator. The recuperator disclosed in this patent has a circular configuration. The recuperator has a plurality of cell made from a pair of primary surface sheets, a plurality of spacer bars and a plurality of guide strips. The component parts are welded together to form the recuperator. The welding of these thin sheet and component parts into a cell having a sealed interface is difficult to accomplish in a cost effective and efficient manner.
During the assembly of the cells and the recuperator, the interface of the components are positioned one with respect to another in a preestablished relationship and are welded together. The effectiveness of the positioning and holding process during the welding process used to form the cells is in many instances dependent on the ability to maintain the relationship of the components one to another. The result of maintaining the components relationship may results in a defective cell. For example, in some defective cells the components relationship can result in defective welding and leakage between the donor side and the recipient side. Thus, an effective and efficient process is needed to insure the position and location of the component relationship prior to final welding and during assembly.
The present invention is directed to overcome one or more of the problems as set forth above.
In one aspect of the invention a method of aligning a plurality of cells forms a recuperator core. The recuperator core has a circular configuration and defines an axis xe2x80x9cAxe2x80x9d about which is formed an inner diameter xe2x80x9cIDxe2x80x9d and an outer diameter xe2x80x9cODxe2x80x9d. A method of aligning comprises positioning an inner sealing ring about an inner chucking portion; aligning a first end of the inner sealing ring with an end of the inner chucking portion; expanding the inner chucking portion into an expanded position maintaining the first end of the inner sealing ring flush with the end of the inner chucking portion, the inner sealing ring being centered about the axis xe2x80x9cAxe2x80x9d; positioning an upper portion about the inner chucking portion, the upper portion being in a loading position; positioning a preestablished quantity of the plurality of cells within the upper portion in a preestablished relationship; and moving the upper portion from the loading position to a clamping position and properly aligning each of the plurality of cell one to another.